A 4"" PNEUMATIC LINE WAS PLUGGED WITH TALC. A 3/8"" HIGH-PRESSURE AIR HOSE WAS USED TO PRESSURIZE THE LINE USING A MORRIS COUPLING. THE PRESSURE BLEW THE COUPLING AND NIPPLE OFF THE END OF TH E LINE TOWARDS THE EE, HITTING HIS LEFT FOREARM AND STRIKING IT AGAINST THE END OF THE OTHER PIPE. EXAMINED ON 11-21-03 AS HAVING REACHED MAXIMUM MEDICAL IMPROVEMENT (MMI) WITH 0% IMPAIRMENT.